In the process of flexographic printing, or flexography, ink is transferred by an ink transfer roller from an ink source to a flexible printing plate or roller. The ink transfer roller is provided on its cylindrical surface with an array of small depressions or indentations called cells. The array of cells on the surface of the ink transfer roller is known as a screen. The screen receives and holds ink from a supply source, a scraper blade or a rubber roller removes excess ink from the surface of the roller, and the ink from the screen is then transferred, directly or indirectly to the flexographic printing plate or roller.
The ink transfer rollers are produced by forming a roller with a smooth cylindrical surface of a suitable material, usually a metal such as copper, and then forming a screen thereon. The screen is normally formed by rotating the ink transfer roller, bringing a rotatable screen forming tool into contact with the surface of the roller such that it rotates about an axis substantially parallel to the axis of the transfer roller and moving the rotating tool along the roller such that a helical path of cells is formed with adjacent turns of the helix in register.
The present invention provides an alternative to the conventional apparatus for the screening of ink transfer rollers i.e. forming a screen of cells on the cylindrical surface of the ink transfer roller.